[PATCH v2] of: check previous kernel's ima-kexec-buffer against memory bounds

Vaibhav Jain posted 1 patch 1 month ago
drivers/of/kexec.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
[PATCH v2] of: check previous kernel's ima-kexec-buffer against memory bounds
Posted by Vaibhav Jain 1 month ago
Presently ima_get_kexec_buffer() doesn't check if the previous kernel's
ima-kexec-buffer lies outside the addressable memory range. This can result
in a kernel panic if the new kernel is booted with 'mem=X' arg and the
ima-kexec-buffer was allocated beyond that range by the previous kernel.
The panic is usually of the form below:

$ sudo kexec --initrd initrd vmlinux --append='mem=16G'

<snip>
 BUG: Unable to handle kernel data access on read at 0xc000c01fff7f0000
 Faulting instruction address: 0xc000000000837974
 Oops: Kernel access of bad area, sig: 11 [#1]
<snip>
 NIP [c000000000837974] ima_restore_measurement_list+0x94/0x6c0
 LR [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160
 Call Trace:
 [c00000000371fa80] [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160
 [c00000000371fb00] [c0000000020512c4] ima_init+0x80/0x108
 [c00000000371fb70] [c0000000020514dc] init_ima+0x4c/0x120
 [c00000000371fbf0] [c000000000012240] do_one_initcall+0x60/0x2c0
 [c00000000371fcc0] [c000000002004ad0] kernel_init_freeable+0x344/0x3ec
 [c00000000371fda0] [c0000000000128a4] kernel_init+0x34/0x1b0
 [c00000000371fe10] [c00000000000ce64] ret_from_kernel_thread+0x5c/0x64
 Instruction dump:
 f92100b8 f92100c0 90e10090 910100a0 4182050c 282a0017 3bc00000 40810330
 7c0802a6 fb610198 7c9b2378 f80101d0 <a1240000> 2c090001 40820614 e9240010
 ---[ end trace 0000000000000000 ]---

Fix this issue by checking returned PFN range of previous kernel's
ima-kexec-buffer with pfn_valid to ensure correct memory bounds.

Fixes: 467d27824920 ("powerpc: ima: get the kexec buffer passed by the previous kernel")
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Prakhar Srivastava <prsriva@linux.microsoft.com>
Cc: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>

---
Changelog
==========

v2:
* Instead of using memblock to determine the valid bounds use pfn_valid() to do
so since memblock may not be available late after the kernel init. [ Mpe ]
* Changed the patch prefix from 'powerpc' to 'of' [ Mpe ]
* Updated the 'Fixes' tag to point to correct commit that introduced this
function. [ Rob ]
* Fixed some whitespace/tab issues in the patch description [ Rob ]
* Added another check for checking ig 'tmp_size' for ima-kexec-buffer is > 0
---
 drivers/of/kexec.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
index 8d374cc552be..879e984fe901 100644
--- a/drivers/of/kexec.c
+++ b/drivers/of/kexec.c
@@ -126,6 +126,7 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
 {
 	int ret, len;
 	unsigned long tmp_addr;
+	unsigned int start_pfn, end_pfn;
 	size_t tmp_size;
 	const void *prop;
 
@@ -140,6 +141,22 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
 	if (ret)
 		return ret;
 
+	/* Do some sanity on the returned size for the ima-kexec buffer */
+	if (!tmp_size)
+		return -ENOENT;
+
+	/*
+	 * Calculate the PFNs for the buffer and ensure
+	 * they are with in addressable memory.
+	 */
+	start_pfn = PHYS_PFN(tmp_addr);
+	end_pfn = PHYS_PFN(tmp_addr + tmp_size - 1);
+	if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn)) {
+		pr_warn("IMA buffer at 0x%lx, size = 0x%zx beyond memory\n",
+			tmp_addr, tmp_size);
+		return -EINVAL;
+	}
+
 	*addr = __va(tmp_addr);
 	*size = tmp_size;
 
-- 
2.35.1
Re: [PATCH v2] of: check previous kernel's ima-kexec-buffer against memory bounds
Posted by Rob Herring 1 month ago
On Tue, May 24, 2022 at 11:20:42AM +0530, Vaibhav Jain wrote:
> Presently ima_get_kexec_buffer() doesn't check if the previous kernel's
> ima-kexec-buffer lies outside the addressable memory range. This can result
> in a kernel panic if the new kernel is booted with 'mem=X' arg and the
> ima-kexec-buffer was allocated beyond that range by the previous kernel.
> The panic is usually of the form below:
> 
> $ sudo kexec --initrd initrd vmlinux --append='mem=16G'
> 
> <snip>
>  BUG: Unable to handle kernel data access on read at 0xc000c01fff7f0000
>  Faulting instruction address: 0xc000000000837974
>  Oops: Kernel access of bad area, sig: 11 [#1]
> <snip>
>  NIP [c000000000837974] ima_restore_measurement_list+0x94/0x6c0
>  LR [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160
>  Call Trace:
>  [c00000000371fa80] [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160
>  [c00000000371fb00] [c0000000020512c4] ima_init+0x80/0x108
>  [c00000000371fb70] [c0000000020514dc] init_ima+0x4c/0x120
>  [c00000000371fbf0] [c000000000012240] do_one_initcall+0x60/0x2c0
>  [c00000000371fcc0] [c000000002004ad0] kernel_init_freeable+0x344/0x3ec
>  [c00000000371fda0] [c0000000000128a4] kernel_init+0x34/0x1b0
>  [c00000000371fe10] [c00000000000ce64] ret_from_kernel_thread+0x5c/0x64
>  Instruction dump:
>  f92100b8 f92100c0 90e10090 910100a0 4182050c 282a0017 3bc00000 40810330
>  7c0802a6 fb610198 7c9b2378 f80101d0 <a1240000> 2c090001 40820614 e9240010
>  ---[ end trace 0000000000000000 ]---
> 
> Fix this issue by checking returned PFN range of previous kernel's
> ima-kexec-buffer with pfn_valid to ensure correct memory bounds.
> 
> Fixes: 467d27824920 ("powerpc: ima: get the kexec buffer passed by the previous kernel")
> Cc: Frank Rowand <frowand.list@gmail.com>
> Cc: Prakhar Srivastava <prsriva@linux.microsoft.com>
> Cc: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> Cc: Rob Herring <robh@kernel.org>
> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
> 
> ---
> Changelog
> ==========
> 
> v2:
> * Instead of using memblock to determine the valid bounds use pfn_valid() to do
> so since memblock may not be available late after the kernel init. [ Mpe ]
> * Changed the patch prefix from 'powerpc' to 'of' [ Mpe ]
> * Updated the 'Fixes' tag to point to correct commit that introduced this
> function. [ Rob ]
> * Fixed some whitespace/tab issues in the patch description [ Rob ]
> * Added another check for checking ig 'tmp_size' for ima-kexec-buffer is > 0
> ---
>  drivers/of/kexec.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
> index 8d374cc552be..879e984fe901 100644
> --- a/drivers/of/kexec.c
> +++ b/drivers/of/kexec.c
> @@ -126,6 +126,7 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
>  {
>  	int ret, len;
>  	unsigned long tmp_addr;
> +	unsigned int start_pfn, end_pfn;
>  	size_t tmp_size;
>  	const void *prop;
>  
> @@ -140,6 +141,22 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
>  	if (ret)
>  		return ret;
>  
> +	/* Do some sanity on the returned size for the ima-kexec buffer */
> +	if (!tmp_size)
> +		return -ENOENT;
> +
> +	/*
> +	 * Calculate the PFNs for the buffer and ensure
> +	 * they are with in addressable memory.
> +	 */
> +	start_pfn = PHYS_PFN(tmp_addr);
> +	end_pfn = PHYS_PFN(tmp_addr + tmp_size - 1);
> +	if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn)) {

pfn_valid() isn't necessarily RAM, only that you have a struct page 
AIUI. Maybe page_is_ram() instead?

Thanks to Robin for this.

Rob
Re: [PATCH v2] of: check previous kernel's ima-kexec-buffer against memory bounds
Posted by Vaibhav Jain 3 weeks, 5 days ago
Thanks for looking into this patch Rob,

I have addressed your review comment in v3 of the patch posted at
https://lore.kernel.org/all/20220531041446.3334259-1-vaibhav@linux.ibm.com/

<snip>

-- 
Cheers
~ Vaibhav
Re: [PATCH v2] of: check previous kernel's ima-kexec-buffer against memory bounds
Posted by Ritesh Harjani 1 month ago
Just a minor nit which I noticed.

On 22/05/24 11:20AM, Vaibhav Jain wrote:
> Presently ima_get_kexec_buffer() doesn't check if the previous kernel's
> ima-kexec-buffer lies outside the addressable memory range. This can result
> in a kernel panic if the new kernel is booted with 'mem=X' arg and the
> ima-kexec-buffer was allocated beyond that range by the previous kernel.
> The panic is usually of the form below:
>
> $ sudo kexec --initrd initrd vmlinux --append='mem=16G'
>
> <snip>
>  BUG: Unable to handle kernel data access on read at 0xc000c01fff7f0000
>  Faulting instruction address: 0xc000000000837974
>  Oops: Kernel access of bad area, sig: 11 [#1]
> <snip>
>  NIP [c000000000837974] ima_restore_measurement_list+0x94/0x6c0
>  LR [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160
>  Call Trace:
>  [c00000000371fa80] [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160
>  [c00000000371fb00] [c0000000020512c4] ima_init+0x80/0x108
>  [c00000000371fb70] [c0000000020514dc] init_ima+0x4c/0x120
>  [c00000000371fbf0] [c000000000012240] do_one_initcall+0x60/0x2c0
>  [c00000000371fcc0] [c000000002004ad0] kernel_init_freeable+0x344/0x3ec
>  [c00000000371fda0] [c0000000000128a4] kernel_init+0x34/0x1b0
>  [c00000000371fe10] [c00000000000ce64] ret_from_kernel_thread+0x5c/0x64
>  Instruction dump:
>  f92100b8 f92100c0 90e10090 910100a0 4182050c 282a0017 3bc00000 40810330
>  7c0802a6 fb610198 7c9b2378 f80101d0 <a1240000> 2c090001 40820614 e9240010
>  ---[ end trace 0000000000000000 ]---
>
> Fix this issue by checking returned PFN range of previous kernel's
> ima-kexec-buffer with pfn_valid to ensure correct memory bounds.
>
> Fixes: 467d27824920 ("powerpc: ima: get the kexec buffer passed by the previous kernel")
> Cc: Frank Rowand <frowand.list@gmail.com>
> Cc: Prakhar Srivastava <prsriva@linux.microsoft.com>
> Cc: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> Cc: Rob Herring <robh@kernel.org>
> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
>
> ---
> Changelog
> ==========
>
> v2:
> * Instead of using memblock to determine the valid bounds use pfn_valid() to do
> so since memblock may not be available late after the kernel init. [ Mpe ]
> * Changed the patch prefix from 'powerpc' to 'of' [ Mpe ]
> * Updated the 'Fixes' tag to point to correct commit that introduced this
> function. [ Rob ]
> * Fixed some whitespace/tab issues in the patch description [ Rob ]
> * Added another check for checking ig 'tmp_size' for ima-kexec-buffer is > 0
> ---
>  drivers/of/kexec.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>
> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
> index 8d374cc552be..879e984fe901 100644
> --- a/drivers/of/kexec.c
> +++ b/drivers/of/kexec.c
> @@ -126,6 +126,7 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
>  {
>  	int ret, len;
>  	unsigned long tmp_addr;
> +	unsigned int start_pfn, end_pfn;

^^^ Shouldn't this be unsigned long?

-ritesh

>  	size_t tmp_size;
>  	const void *prop;
>
> @@ -140,6 +141,22 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
>  	if (ret)
>  		return ret;
>
> +	/* Do some sanity on the returned size for the ima-kexec buffer */
> +	if (!tmp_size)
> +		return -ENOENT;
> +
> +	/*
> +	 * Calculate the PFNs for the buffer and ensure
> +	 * they are with in addressable memory.
> +	 */
> +	start_pfn = PHYS_PFN(tmp_addr);
> +	end_pfn = PHYS_PFN(tmp_addr + tmp_size - 1);
> +	if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn)) {
> +		pr_warn("IMA buffer at 0x%lx, size = 0x%zx beyond memory\n",
> +			tmp_addr, tmp_size);
> +		return -EINVAL;
> +	}
> +
>  	*addr = __va(tmp_addr);
>  	*size = tmp_size;
>
> --
> 2.35.1
>
Re: [PATCH v2] of: check previous kernel's ima-kexec-buffer against memory bounds
Posted by Vaibhav Jain 1 month ago
Hi Ritesh,
thanks for looking into this patch,

Ritesh Harjani <ritesh.list@gmail.com> writes:

> Just a minor nit which I noticed.
>
> On 22/05/24 11:20AM, Vaibhav Jain wrote:
>> Presently ima_get_kexec_buffer() doesn't check if the previous kernel's
>> ima-kexec-buffer lies outside the addressable memory range. This can result
>> in a kernel panic if the new kernel is booted with 'mem=X' arg and the
>> ima-kexec-buffer was allocated beyond that range by the previous kernel.
>> The panic is usually of the form below:
>>
>> $ sudo kexec --initrd initrd vmlinux --append='mem=16G'
>>
>> <snip>
>>  BUG: Unable to handle kernel data access on read at 0xc000c01fff7f0000
>>  Faulting instruction address: 0xc000000000837974
>>  Oops: Kernel access of bad area, sig: 11 [#1]
>> <snip>
>>  NIP [c000000000837974] ima_restore_measurement_list+0x94/0x6c0
>>  LR [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160
>>  Call Trace:
>>  [c00000000371fa80] [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160
>>  [c00000000371fb00] [c0000000020512c4] ima_init+0x80/0x108
>>  [c00000000371fb70] [c0000000020514dc] init_ima+0x4c/0x120
>>  [c00000000371fbf0] [c000000000012240] do_one_initcall+0x60/0x2c0
>>  [c00000000371fcc0] [c000000002004ad0] kernel_init_freeable+0x344/0x3ec
>>  [c00000000371fda0] [c0000000000128a4] kernel_init+0x34/0x1b0
>>  [c00000000371fe10] [c00000000000ce64] ret_from_kernel_thread+0x5c/0x64
>>  Instruction dump:
>>  f92100b8 f92100c0 90e10090 910100a0 4182050c 282a0017 3bc00000 40810330
>>  7c0802a6 fb610198 7c9b2378 f80101d0 <a1240000> 2c090001 40820614 e9240010
>>  ---[ end trace 0000000000000000 ]---
>>
>> Fix this issue by checking returned PFN range of previous kernel's
>> ima-kexec-buffer with pfn_valid to ensure correct memory bounds.
>>
>> Fixes: 467d27824920 ("powerpc: ima: get the kexec buffer passed by the previous kernel")
>> Cc: Frank Rowand <frowand.list@gmail.com>
>> Cc: Prakhar Srivastava <prsriva@linux.microsoft.com>
>> Cc: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
>> Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com>
>> Cc: Rob Herring <robh@kernel.org>
>> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
>>
>> ---
>> Changelog
>> ==========
>>
>> v2:
>> * Instead of using memblock to determine the valid bounds use pfn_valid() to do
>> so since memblock may not be available late after the kernel init. [ Mpe ]
>> * Changed the patch prefix from 'powerpc' to 'of' [ Mpe ]
>> * Updated the 'Fixes' tag to point to correct commit that introduced this
>> function. [ Rob ]
>> * Fixed some whitespace/tab issues in the patch description [ Rob ]
>> * Added another check for checking ig 'tmp_size' for ima-kexec-buffer is > 0
>> ---
>>  drivers/of/kexec.c | 17 +++++++++++++++++
>>  1 file changed, 17 insertions(+)
>>
>> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
>> index 8d374cc552be..879e984fe901 100644
>> --- a/drivers/of/kexec.c
>> +++ b/drivers/of/kexec.c
>> @@ -126,6 +126,7 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
>>  {
>>  	int ret, len;
>>  	unsigned long tmp_addr;
>> +	unsigned int start_pfn, end_pfn;
>
> ^^^ Shouldn't this be unsigned long?
Thanks for catching this. Yes that should be 'unsigned long'. Will
resend the patch with this fixed.

>
> -ritesh
>
>>  	size_t tmp_size;
>>  	const void *prop;
>>
>> @@ -140,6 +141,22 @@ int ima_get_kexec_buffer(void **addr, size_t *size)
>>  	if (ret)
>>  		return ret;
>>
>> +	/* Do some sanity on the returned size for the ima-kexec buffer */
>> +	if (!tmp_size)
>> +		return -ENOENT;
>> +
>> +	/*
>> +	 * Calculate the PFNs for the buffer and ensure
>> +	 * they are with in addressable memory.
>> +	 */
>> +	start_pfn = PHYS_PFN(tmp_addr);
>> +	end_pfn = PHYS_PFN(tmp_addr + tmp_size - 1);
>> +	if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn)) {
>> +		pr_warn("IMA buffer at 0x%lx, size = 0x%zx beyond memory\n",
>> +			tmp_addr, tmp_size);
>> +		return -EINVAL;
>> +	}
>> +
>>  	*addr = __va(tmp_addr);
>>  	*size = tmp_size;
>>
>> --
>> 2.35.1
>>

-- 
Cheers
~ Vaibhav